Notes : (From James Taylor) The only place in Japan (and hence the world) to offer this machine was Karaoke room 'Big Echo Shibuya'. Their site is here.

I called to ask about the room so me and my friends could go see it and play, but as it happens, all of the machines were decomissioned due to lack of support from konami when things broke on the machine. They also confirmed that they were the only karaoke room in Japan to have the DDRKaraoke mix. It appears that the machines were either junked or put into storage, so they are completely unavailable now it seems unfortunately.